An inkjet printing device known in the art prints images by executing main scans (called “passes”) to move a print head over a sheet of paper in a main scanning direction while ejecting ink droplets from the print head onto the paper to form dots (printed pixels). Also known in the art are laser printers that irradiate a laser beam onto a photosensitive drum to form an electrostatic latent image for each main scan line following the main scanning direction of the laser beam, and that transfers toner deposited in the electrostatic latent image onto a printing medium. In either type of printing device, the quality of the printed image can suffer when the positions of the printed pixels (the pixel positions on the printing medium) deviate from the intended positions. To prevent this type of drop in image quality, a technology has been proposed for an inkjet printing device in which a plurality of evaluation images is printed while varying the timing at which ink droplets are ejected during main scans.